Discussion in 'Electronic Repairs & Modifications, DIY' started by aseman, Jul 12, 2011.
How can we correct weak metalization in PCB plating???
I am not a PCB manufacturing expert....what are you trying to do, re-plate though holes? Or its the trace and planes you need more copper for?
Actually we have had this problem since the temprature is increased about one month ago . and we had this problem last year .
The matter of fact is the surface of board is metalized well just the metalization in the holes are weak .
We check all of the process such as cleaning , micro-etch, pre - active and specially activation stage. In spite of those stages are correct analitically but some of the holes are weak.
Could you please help us ?
We can discribe more if nessesary.
More description would be helpful.
Can you clarify - is this you operating your own PCB manufacture equipment, or are you having problems with a 3rd-party PCB manufacturer? When you say the holes are "weak", do you mean they fail under stress or that the plating-through does not happen uniformly?
Is it FR4 board? How many layers? What weight of copper are you using? What's the diameter of the via holes? Do you get adequate plating of any larger diameter component holes?
Yes, actually we receive the orders of customers and we manufacture the PCB by ourselves in factory.
We plated the boards in this way : cleaning by an acidic cleaner solution - micro etch - pre activation - activation - copper electroless - copper plating .
In answer about your questions:
1 . The plating-through does not happen uniformly, somewhere has not any covering and somewhere is weak.
2 . The boards are 2 - 4 layers.
3 . The thickness of copper is approx 0.3 - 0.4 Micron.
4 . The diameters of holes are different, between 1 - 3 mm.
The strange thing is that when we have increased the concentration of components of bath, specially Formaldehid and NaOH, the problem has been solved somewhat. But why it happened? While we adjusted the bath at the optimum range before the whether gets hot, we have not any problem.
I have mentioned before that this problem has been started exactly when the temperature has increased . Please pay attention.
We hope that we can clarify . If anything is unclear , please inform us.
"I have mentioned before that this problem has been started exactly when the temperature has increased . Please pay attention. "
Really do not help.
Its sound to me, YOU ARE THE PROFESSIONAL here, why don't you figure it out. And if you have figured it out, why are you posting a question here?
Please let me remind you that this is a audio engineering forum, specifically audio equipment designers forum, not PCB manufacturing forum.
I didn't read anything into that other than the OP being a non-native English speaker. What I assumed he meant was "Note that, as I mentioned earlier, the problem did not start until the temperature was increased".
On the other hand, I don't think a PCB professional would ever say a board's copper thickness was 0.3 - 0.4 micron, as these are the sort of geometries used in analog integrated circuits. By way of comparison, the standard 1 oz copper on a PCB has a thickness of about 35 micron.
Fair Enough, maybe I read more into it than was there, maybe I am having a bad day....but I am with you on the .3-.4 micron I don't get that either.
Thank you for attention
Back in 1979, while working for the Scully Corporation, there were certain issues with PCB plate through. Some of these holes had extremely tiny springlike coils of wire inserted within the holes. When the parts were inserted & soldered, these microsized wire coils ensured proper continuity between the top & bottom traces. This was in and above the plating process alone. And circuit board technologies have changed considerably since 1979 of which I have not kept up with.
I am sure thermal characteristics are also a factor when soldering with different alloys other than lead. There are many greener countries today that have deemed lead illegal. I really hated trying to solder with that aluminum/tin when I was in New Zealand back in 1989. It was nearly impossible to contend with. I actually brought it back with me to make sure I never purchased anything like that again here in the USA. When the time comes, I'll probably purchase myself at least 50 pounds of 60/40 lead-based rosin core solder. That should last me for my ever decreasing time in this industry? Maybe one day it will be as valuable as gold and alchemy will become a reality?
I am alchemy out of my mind
Mx. Remy Ann David
I'm new to this forum and was really looking for DIY NEVE type pre's when i ran across this thread. I was a Quality Manager in several Mil spec & ISO 9K certified electronic assembly plants. I worked for a few years in a PCB mfg facility. I was the supervisor in the cross section lab. 98% of all the panels were MIL-55110 and other MIL & Aerospace specs. The boards were anywhere from simple, single sided to 24 layers with 4mm, laser etched vias. I actually did cross sections of these vias. A typical PCB in a class 2 IPC would consist of .062 component PTH's with .5 oz copper traces 4-6 mil line width & spacing. Ground traces could be 1 oz copper or .5 oz on ground shields, etc.
Have you checked the temp of your hot air knife during hot air solder leveling? Do you monitor this process? How often do you clean the pot and replace solder? Is the HASL oil based or dry?
If you're working with 4-6 layer boards, .062 thickness, what specifications are you building to? IPC-A-600? MIL-55110? How often do you check your etching tanks for proper chemical balance? If the PTH's are thin, have you checked for drill smear? Nail heading in the cross section will reveal drill smear. Mil & class 3 IPC allows 150% nail heading
It sounds like you have some contamination going on if solder is not adhering to copper or copper to layers. Do you check the raw panels before pressing? After drill? Do you do coupons on the panel? Do you cross section the coupons post drill to verify no smear? How many hits do you allow during drill before changing bits?
Perhaps you should do cross sections after etch and after drill to verify your process. If there is drill smear or nail heading, change the bits and cross section again after changing the bits. Take that panel to etch and run it thru the process then cross section again and check wall thickness under 400X scope. Don't forget to Solder the holes before mounting for heat stress.
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